Communication method, mobile network system and device

ABSTRACT

A mobile communication system, comprising a user equipment (UE), a mobility management entity (MME), and a mobile switching center/visited location register (MSC/VLR), wherein the MME, upon reception of an SGsAP-PAGING-REQUEST message regarding an international mobile-station subscription identifier (IMSI) from the MSC/VLR as a paging request message, sends the paging request message including location information provided by the MSC/VLR to page the UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of co-pending application Ser. No.13/421,575 filed on Mar. 15, 2012, which is a division of co-pendingapplication Ser. No. 13/381,746 filed on Dec. 30, 2011, which is aNational Stage of International Application No. PCT/JP2011/060215 filedon Apr. 27, 2011, which claims foreign priority to Japanese PatentApplication No. 2010-102166 filed on Apr. 27, 2010. Abandonedapplication Ser. Nos. 13/421,602, 13/421,621 and 13/421,641, all filedon Mar. 15, 2012 are also divisions of and claim priority to applicationSer. No. 13/381,746. Co-pending application Ser. No. 13/421,586, filedMar. 15, 2012 is also a division of and claims priority to applicationSer. No. 13/381,746. Patent application Ser. No. 13/421,628, filed onMar. 15, 2012 is also a division of and claims priority to applicationSer. No. 13/381,746. The total contents of disclosure of the patentapplication of the senior filing date are to be incorporated byreference into the present application.

TECHNICAL FIELD

This invention relates to a communication network and, moreparticularly, to a system and a method as well as an apparatus that maybe applied to advantage to the next-generation mobile network system EPC(Evolved Packet Core).

The following recites certain abbreviations used in the presentspecification.

CS: Circuit Switched

CSFB: Circuit Switched Fall Back

eNodeB (eNB): evolved NodeB

G-MSC: Gateway Mobile Switch Center

GPRS: General Packet Radio Service

GTP-C: (GPRS Tunneling Protocol Control Plane)

GTP-U: (GPRS Tunneling Protocol User Plane)

P-MIP: Proxy Mobile Internet Protocol

HSS: Home Subscriber Server

IMS: IP Multimedia Subsystem

IMSI: International Mobile-Station Subscription Identifier

ISR: Idlemode Signaling Reduction

LTE: Long Term Evolution

MME: Mobility Management Entity

MSC: Mobile Switching Center

MTC: Machine type communication

P-GW: (PGW or PDN-GW): Packet Data Network Gateway

PDN: Packet Data Network

QCI: QoS Class Identifier

RAI: Routing Area Identity

RNC: Radio Network Controller

S-GW (or SGW): Serving Gateway

SGSN: Serving GPRS Support Node

SMS: Short Message Service

SCPT: Stream Control Transmission Protocol

TA List: Tracking Area List

TAU: Tracking Area Update

TEID: Tunnel Endpoint Identifier

GRE key: Generic Routing Encapsulation Key

UE: User Equipment

UMTS: Universal Mobile Telecommunications System

VLR: Visited Location Register

3G: Third Generation

3GPP: 3rd Generation Partnership Project

BACKGROUND ART

The next-generation mobile network system EPC is a network architecturethat accommodates 3G (third generation mobile phone communicationsystem), LTE and so forth in one network. The following describesseveral network nodes.

A MME is a mobility management node. In LTE radio access, the MME takescharge of mobility management (mobility control), such as tracking, ofan idle-mode mobile station UE, authentication and setting up a userdata forwarding path between an S-GW and a base station eNodeB, in LTEradio access. A mobile station is also termed ‘a user apparatus’, ‘amobile terminal’ or simply ‘a terminal’. The MME is involved in trackingand paging of idle-mode UEs or in bearer activate/deactivate processes.The MME selects the S-GW at the time of handover of the UE in LTE andperforms user authentication along with HSS. It is noted that a bearermeans a logical packet transmission path set up between eNodeB andS-GW/P-GW or the like.

An SGSN is a mobility management node in the 3G core network. It is apacket switching unit that takes charge of mobility management formobile stations, such as serving subscriber management, servingsubscriber mobility management, originating/incoming call control,tunneling control, charging control, QoS (Quality of Service) control orthe like.

When a mobile terminal (UE) is in an idle or power-saving state(LTE-idle) in an LTE core network, the mobile station (UE) is identifiedat the accuracy corresponding to a tracking area list (TA List) composedof a plurality of cells (MME maintains the latest updated TA List). Atthe time of an incoming call to the mobile station, paging is performedusing the latest TA List registered last time. The SGSN of the 3G corenetwork performs paging in an RA (Routing Area).

An S-GW performs routing and forwarding of a user data packet. The S-GWis a bearer management node that manages context of a mobile station UE(a parameter of IP bearer service or the like). In response to a bearersetting request from an MME that has received an attach request from amobile station UE, The S-GW sets a path setting request for a P-GW andbearer in the direction of an eNode. The S-GW also performs triggeringof a paging when the downlink (DL) data to a terminal has arrived.)

A P-GW takes charge of connection of a mobile station (also termed a UE,a user apparatus or a mobile terminal) to a packet data network (aservice network: Web browsing service or an external network, such asIMS or the like.

The following describes restarting of MME/SGSN.

The ‘restart’ or ‘restart of MME/SGSN’ means cessation of service due tofailure, or intentional cessation of service for maintenance, that leadsto initialization setting operation in the MME/SGSN, as a result ofwhich, subscriber information or bearer information that is necessaryfor the MME/SGSN operation to operate is lost.

Non-Patent Document 2 (3GPP TS 23.007) provides that, when the S-GWdetects that an MME/SGSN has restarted, the S-GW is to release bearercontext of a mobile station UE registered in the MME/SGSN that hasrestarted. That is, According to Non-Patent Document 2, when the MMEre-starts after failure, the MME removes the entirety of bearer contextsaffected by the restarting. When the S-GW detects that the MME hasrestarted, the S-GW removes PDN connection table/bearer contextcorresponding to the MME that has restarted and releases inner resourcesrelevant to the PND connection.

Assuming that an S-GW operates in accordance with the abovespecification of the Non-Patent Document 2, when the MME operation hasrestarted, the S-GW is unable to effect a packet incoming operation to amobile station UE until originating a call by the mobile station itselfor periodic location registration (e.g., Attach/TAU Request)periodically by performed by the mobile station itself to the MME.

When there is an incoming call to the mobile station UE, the networkperforms paging all at once to whole cells associated with an area wherethe mobile station UE has made location registration (tracking area).The so paged mobile station UE accesses a serving cell and establishes acall. However, according to the specification of Non-Patent Document 2,the entirety of bearer information or resources of the restarted MME hasalready been removed or released. That is, in the S-GW, radio accessbearers in the direction of from the S-GW to the eNodeB and sessioninformation between the MME and the S-GW have been removed or released,so that when the incoming packet data to the mobile station LIE isreceived only to no effect.

In the S-GW in this state, TEID or GRE Key, as the identificationinformation of a tunnel (GTP-U or P-MIP), a transport protocol betweenthe S-GW and the P-GW, also has been removed. Hence, in the S-GW, theincoming data is rejected. The P-GW also removes relevant resources inresponse to the rejection of the incoming packet data from the S-GW.

PRIOR ART DOCUMENT Patent Document Non-Patent Document 1:

-   3GPP TS 23.203 V9.4.0 (2010 March) 3rd Generation Partnership    Project: Technical Specification Group Services and System Aspects:    Policy and charging control architecture (Release 9), page 31, Table    6.1.7: Standardized QCI characteristics

Non-Patent Document 2:

-   3GPP TS 23.007 V9.3.0 (2010 March) 3rd Generation Partnership    Project: Technical Specification Group Core Network and Terminals;    Restoration procedures (Release 9), pages 27-28 Non-Patent Document    3:-   3GPP TS 23.272 V9.3.0 (2010 March) 3rd Generation Partnership    Project: Technical Specification Group Services and System Aspect;    Circuit Switched (CS) fallback In Evolved Packet System (EPS); Stage    2 (Release 9) pages 26-27

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The disclosures of the Non-Patent Documents 1 to 3 are incorporated byreference into the present specification. The following is an analysisof the related techniques.

In case the S-GW operates in accordance with the above specification ofNon-Patent Document 2, as described above, the S-GW which has detectedthe restarting of the mobility management node MME/SGSN releasesentirety of bearers of the mobile station UE registered in the MME/SGSNwhere restarting occurred.

Hence, the incoming to the mobile station UE after the restarting of themobility management node MME/SGSN may not be informed to the mobilestation UE until such time the attach operation for registration in thenetwork is carried out in the mobile station UE. That is, if, during thetime that elapses after restarting of the MME/SGSN until the end of theattachment operation, triggered by the origination by the mobile stationUE itself or the periodic location registration by the mobile stationUE, the mobile station UE is unable to have a communication service,even if there is an incoming of the communication service. For example,during a time interval of the periodic location registration (e.g., 45minutes), at the maximum, following the restarting of the MME/SGSN,incoming packet data, addressed to the mobile station UE, may not bedelivered to the mobile station UE.

That is, a packet communication service is at a standstill. This poses aserious problem since communication services as social infrastructuremay not be received for a preset time in case IMS is exploited on an EPSnetwork.

Accordingly, it is an object of the present invention to provide asystem, a method and an apparatus which enable to accelerate restorationof communication services for a mobile station after restarting of amobility management node.

Means to Solve the Problems

In accordance with one aspect of the present invention, there isprovided a communication method in which a bearer management nodemaintains a specific bearer eligible for restoration of communicationservices, and removes the other hearers. In case a mobility managementnode is restarted, the bearer management node maintains at least onebearer.

In accordance with another aspect of the present invention, there isprovided a communication method wherein, on restarting of a mobilitymanagement node, a circuit switched node sends to the mobilitymanagement node a notification message including identificationinformation associated with an mobile station and location registrationarea information, and the mobility management node starts paging,inclusive of the identification information associated with the mobilestation, for an area corresponding to the location registration areainformation.

According to the present invention, there is also provided a mobilenetwork system in which a bearer management node maintains a specificbearer eligible for restoration of communication services, and removesother bearers. The mobile network system includes a mobility managementnode and a bearer management node. When restarting of the mobilitymanagement node is performed, the bearer management node maintains atleast one of the bearers as set.

According to the present invention, there is provided a mobile networksystem comprising a mobility management node and a circuit switchednode. In case restarting of the mobility management node is performed,the circuit switched node sends to the mobility management node anotification message inclusive of the identification informationassociated with the mobile station and the location registration areainformation. The management node performs paging including theidentification information associated with the mobile station for anarea corresponding to the location registration area information.

According to the present invention, there is provided a node apparatusthat manages a bearer, wherein the node apparatus maintains a specificbearer eligible for restoration of communication services, and removesother bearers. In case restarting of the mobility management node isperformed, the node apparatus maintains at least one of the bearers asset.

Effect of the Invention

According to the present invention, it is possible to acceleraterestoration of a communication service for a mobile station followingrestarting of a mobility management node.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for illustrating the operation of a mode of thepresent invention.

FIG. 2 is another diagram for illustrating the operation of the mode ofthe present invention.

FIG. 3 is yet another diagram for illustrating the operation of the modeof the present invention.

FIG. 4 is yet another diagram for illustrating the operation of the modeof the present invention.

FIG. 5 is yet another diagram for illustrating the operation of the modeof the present invention.

FIG. 6 is a diagram for illustrating a packet communication network thataccommodates LTE.

FIG. 7 is a diagram for illustrating a packet communication network thataccommodates 2G/3G.

FIG. 8 is a diagram for illustrating a packet communication network thataccommodates LTE and 2G/3G.

FIG. 9 is a diagram for illustrating CSFB (Circuit Switch Fall Back).

FIG. 10 is a diagram for illustrating an example sequence of anexemplary embodiment 1 of the present invention.

FIG. 11 is a diagram for illustrating another example sequence of theexemplary embodiment 1 of the present invention.

FIG. 12 is a diagram for illustrating yet another example sequence ofthe exemplary embodiment 1 of the present invention.

FIG. 13 is a diagram for illustrating an example operating sequence ofan exemplary embodiment 2 of the present invention.

FIG. 14 is a diagram for illustrating another example operating sequenceof the exemplary embodiment 2 of the present invention.

FIG. 15 is a diagram for illustrating yet another example operatingsequence of the exemplary embodiment 2 of the present invention.

FIG. 16 is a diagram for illustrating an example operating sequence ofan exemplary embodiment 3 of the present invention.

FIG. 17 is a diagram for illustrating another example operating sequenceof the exemplary embodiment 3 of the present invention.

FIG. 18 is a diagram for illustrating an example operating sequence ofan exemplary embodiment 4 of the present invention.

FIG. 19 is a diagram for illustrating another example operating sequenceof the exemplary embodiment 4 of the present invention.

FIG. 20 is a diagram for illustrating yet another example operatingsequence of the exemplary embodiment 4 of the present invention.

FIG. 21 is a diagram for illustrating an example operating sequence ofan exemplary embodiment 5 of the present invention.

FIG. 22 is a diagram for illustrating another example operating sequenceof the exemplary embodiment 5 of the present invention.

FIG. 23 is a diagram for illustrating yet another example operatingsequence of the exemplary embodiment 5 of the present invention.

FIG. 24 is a diagram for illustrating an example operating sequence of amode of the present invention.

PREFERRED MODES FOR CARRYING OUT THE INVENTION

In one of preferred modes of the present invention, when a mobilitymanagement node, such as MME/SGSN, has restarted, a bearer managementnode S-GW does not release all of bearers relevant to the mobilitymanagement node MME/SGSN. The bearer management node (S-GW) holds atleast part of or entirety of bearers to continue a packet incomingservice. That is, when the bearer management node, such as S-GW, detectsrestarting of the mobility management node (MME/SGSN), the bearermanagement node confirms that the mobile station UE is accommodated inthe mobility management node (MME/SGSN). In connection with the mobilestation (UE), accommodated in the mobility management node (MME/SGSN),the bearer management node, such as S-GW, retains at least one ofbearers set in a direction from the bearer management node (S-GW)towards the external network, such as PDN. By so doing, the mobilestation (UE) is able to attach to the network, with packet incoming fromthe external network (PDN) to the mobile station (UE) as a trigger,thereby accelerating the restoration of a communication service for themobile station (UE). In one of preferred modes of the present invention,the bearer management node maintains a specific bearer(s) for restoringa communication service, and removes other bearers. In one of preferredmodes of the present invention, when maintaining the specific bearer,the bearer management node may start a timer. On timeout of the timer,the bearer management node may remove bearer resources that have beenmaintained.

In one of preferred modes of the present invention, it is possible toselect those bearers that render services of high reliability afterrestarting of the mobility management node (MME/SGSN). It is thuspossible to suppress consumption of resources of the bearer managementnode (S-GW) as well as to avoid congestion due to concentration oflocation registrations.

In one of preferred modes of the present invention, the bearermanagement node S-GW maintains the location registration areainformation (TA List/RAI) of the mobile station (UE), informed from themobility management node (MME/SGSN), and the identification information(IMSI) associated with the mobile station. After restarting of themobility management node (MME/SGSN), the bearer management node (S-GW)may, on receipt of incoming data to the mobile station (UE), notify thelocation registration area information (TA list/RAI) and theidentification information (IMSI) to the mobility management node(MME/SGSN). The mobility management node (MME/SGSN) may then performpaging, using the identification information (IMSI), for only the areacorresponding to the location registration area in formation (TAlist/RAI). By so doing, it is possible to selectively reduce an areathat is paged by the base station.

FIG. 1 is a diagram for illustrating one of modes of the presentinvention. A mobility management node MME/SGSN that manages registrationinformation of a mobile station UE, notifies the location registrationinformation of the mobile station UE to an S-GW at the outset. The S-GWmaintains the location registration information of the mobile stationUE. The S-GW also maintains bearers between the S-GW and the P-GW.

Restarting occurs at the mobility management node MME/SGSN.

When the S-GW detects, by e.g., health check, that the mobilitymanagement node MME/SGSN has restarted, the S-GW does not release butmaintains bearers that are set between the S-GW and the P-GW. In thiscase, in view of compatibility of the stable system restoration andavailability of communication services, it is possible for the S-GW notto release but continue to maintain those bearers that will provide forhigh availability services. These services may be exemplified bycommunication that is in need of high reliability in accordance with,e.g., of the operator policy, such as voice services provided by IMS.For example, the S-GW may not release but maintain specific S5/S8bearers between the S-GW and the P-GW, necessary for restoration ofservices initiated from the network side, and to remove all the otherS5/S8 bearers.

In an example shown in FIG. 2, when the S-GW detects, by e.g., healthcheck (GTP-echo), that the mobility management node MME/SGSN hasrestarted, the S-GW releases IMS control bearer services, among bearersset between the S-GW and the P-GW, while maintaining just the bearersused for IMS control. By thus applying to just specific services, it isalso possible to gradually restore the MME/SGSN while overload on theentire system is avoided.

FIG. 3 is a diagram for illustrating the case of applying the presentinvention to IMS services. When packet data has arrived, using thebearer held by the S-GW, the packet incoming is notified, along with theIMSI identifying the UE and the location registration area information,registered beforehand in the S-GW, to the MME/SGSN where the restartinghas occurred. The MME/SGSN is thus able to call(page) the UE using theIMSI and the location registration area information. The mobile stationUE that has been paged using the IMSI, performs re-registering (attach)to the MME/SGSN and re-establishes necessary bearers to receive theentirety of packet communication services. Thus, according to a mode ofthe present invention, even if the MME/SGSN restarts, service arrivalmay be notified to the mobile station UE to prompt its attachment to theMME to improve availability of communication services.

According to a mode of the present invention, it is possible to causethe UE to attach to the network, after restarting of the MME/SGSN, withthe incoming of the packet to the UE as a trigger. Packet communicationservices may instantaneously be restored to the UE whose services havebeen started by the arrival of the incoming packet.

In a mode of the present invention, just those bearers that need highreliability may be taken as bearers to be maintained according to thepresent invention. It is thus possible to suppress consumption of S-GWresources as well as congestion due to concentration of locationregistrations. This operation is indispensable especially in case a UEwhere packet communication occurs periodically, as in MTC, isaccommodated. The reason is that, in such case, packet communicationoccurs for many UEs after restarting of the MME/SGSN, and hence thesubscriber recovering operations may occur in a burst fashion, with thepacket communication as a trigger, thus possibly leading to congestionof the system in its entirety.

FIGS. 4 and 5 are diagrams showing an example in which the presentinvention is applied to CSFB. The CSFB function switches voiceorigination/incoming to 3G to render voice services employing the 3G-CSdomain even in case VoIP services are not provided on LTE. As regardsthe CSFB function, reference is to be made to Non-Patent Document 3(FIGS. 7.2-1 Mobile Termination Call in idle mode).

Referring to FIG. 4, the MME notifies the UE's location registrationinformation to an MSC in advance. When the MME restarts, the MSC detectsthe restarting of the MME by e.g., health check. Referring to FIG. 5,when a call arrived from an originating side G-MSC (CS incoming), theMSC notifies the IMSI and the location registration area to the MME,which MME is able to call (page) the UE using the IMSI and the locationregistration area information.

The following describes exemplary embodiments of the present invention.FIGS. 6 to 9 show networks to which the present invention may beapplied.

Exemplary Embodiment 1

FIG. 6 is a diagram showing a network configuration of an exemplaryembodiment 1 of the present invention. Specifically, FIG. 6 shows apacket communication network that accommodates LTE. Referring to FIG. 6,the network includes a mobile station (UE) 101, a base station (eNodeB)102, a MME 103, an HSS 106, an S-GW 104, a P-GW 105, an external network(PDN) 108 and an IMS 109. The IMS 109 is a communication system thatintegrates packet switched communication services by SIP (SessionInitiation Protocol) to implement multi-media services.

The MME 103 accommodates the eNodeB 102 by an S1-MME interface toperform UE mobility management and authentication as well as setting ofa user forwarding path. The MME 103 refers to the HSS 106 that is adatabase for managing subscriber information, through an S6a interface,to perform e.g., authentication. The MME 103 transmits/receives acontrol signal via S1-MME and S11 interfaces to set up or release theuser forwarding path on an S1-U interface between the eNodeB and theS-GW. The transport protocol at the S1-U interface between the eNodeBand the S-GW is GTP-U.

An S5/S8 interface 107 is an interface (user plane) between S-GW andP-GW. As a transport protocol, a tunneling protocol (GTP-U) or a proxymobile IP protocol (P-MIP), is set.

The S-GW 104 performs user data transmission/reception between it andthe eNodeB 102, while setting up or releasing an external PDN basedtransmission path via P-GW and S5/S8 interface 107. The P-GW 105connects to the external network (PDN) 108 over an SGi interface. Thefollowing describes an operation when the MME restarts.

<First Stage>

FIG. 10 is a sequence diagram that illustrates, as a first stage, astage of registering location registration area information of themobile station UE in the S-GW. In FIG. 10, the base station (eNodeB) 102of FIG. 6 is omitted. It is premised that the mobile station UE1 has setup a radio control link between it and the eNodeB. The respective stepsof FIG. 10 will now be described.

In a step 1 of FIG. 10, the mobile station UE1 transmits a locationregistration request (Attach Request or TAU Request) to the MME1. Notethat, in LTE, the location of the mobile station UE in an idle (standby)mode is managed per location registration area information (trackingarea). Each tracking area corresponds to a location area or a routingarea in 3G/UMTS, and is composed of one or a plurality of cells. In eachof these cells, an identifier of the tracking area to which the cell inquestion belongs is broadcasted. The mobile station in an idle mode hasits location registered in the tracking area in which the mobile stationUE resides, and stores the identifier of the tracking area in which theUE has its location currently registered. When moving from one cell toanother, the mobile station UE receives the identifier of the trackingarea which is broadcasted. In case the identifier of the tracking areabeing broadcasted differs from the identifier of the tracking area,currently registered therein, the UE updates location registration. Arequest for update of this location registration is termed a ‘TAURequest’.

In a step S2 of FIG. 10, the MME1 newly assigns the locationregistration area information (TA List) to the mobile station UE1.

In a step S3 of FIG. 10, the MME1 informs the S-GW1 about the TA List ofthe mobile station UE1 via S11 interface. The S-GW1 stores the TA List,informed from the MME1, in a storage unit (memory) in the S-GW1, as theregistration information of the mobile station UE1.

It is noted that the location registration operation in the steps 1 and2 of FIG. 10 is known per se and is not directly relevant to thesubject-matter of the present invention. Hence, the operation is notexplained in detail.

<Second Stage>

FIG. 11 is a sequence diagram for illustrating, as a second stage, thestage of maintaining a bearer. In a step 1 of FIG. 11, the mobilestation UE1 has already attached to the MME1 (an attach request hasalready been issued). A variety of bearers have already been set upusing S-GW1 and P-GW1.

In a step 2 of FIG. 11, the restarting of the MME1 occurs and in thisMME1, the registration information of the UE1, already attached, iserased.

In a step 3 of FIG. 11, the S-GW1 detects the restarting of the MME1,from processing such as a health check by GTP Echo processing.

In a step 4 of FIG. 11, S-GW1 recognizes all mobile stations UE attachedto the MME1 (it is confirmed that the UE 1 is accommodated in the MME1).

In case the present invention is provided for the entirety of theservices, all bearers related with the mobile station UE1 from the S-GW1towards the external network IMS 1 are maintained in the step S5 of FIG.11.

In steps 6 and 7 of FIG. 11, in distinction from the step S5 of FIG. 11,the bearer maintaining function according to the present invention isnot provided for all services relating to the mobile station UE1, suchthat bearers (bearers used for IMS control) are maintained for specificservices (IMS services providing e.g., voice services).

After confirming in the step S4 of FIG. 11 that the mobile station UE1has been accommodated in the MME1, the S-GW1 further confirms, in thestep 6 of FIG. 11, whether or not there is a bearer(s) providing the IMS(bearer(s) used for IMS control) among the bearers owned by the mobilestation UE1. In verifying the bearers used for IMS control in thismanner, a QCI (QoS Class Identifier) value, which is among informationelements that each bearer has, may be used. If, in using the QCI value,it is ‘5’, for example, the bearer may be concluded to be the bearer(s)used for IMS control (IMS Signaling), in accordance with the Table 6.1.7of Non-Patent Document 1 (3GPP TS23.03). The bearer may then beconcluded to be a control bearer used for rendering voice services.

If there is the bearer(s) used for IMS control among the bearersrelating to the mobile station UE1 managed by the S-GW1, only therelevant bearer(s) are maintained. The remaining bearers are locallyreleased in accordance with the operation in accordance with Non-PatentDocument 2 (3GPP TS23.007).

In case of maintaining the bearers used for IMS control (specificbearers), the S-GW1 starts the operation of a timer to release (remove)relevant bearer resources on timeout, in consideration of a case wherethe mobile station UE1 has already re-attached to another S-GW. Thistimer controls a time of maintaining the above mentioned specific bearerby the S-GW1, and becomes necessary to prevent failing to release thebearers that the S-GW1 maintains. If, in the above timer, the timeequivalent to the time of a periodic location registration timer ownedby the mobile station UE1 is set, the S-GW1 may wait for incoming ofvoice services for a necessary minimum time interval corresponding tothe time of the next periodic location registration request from theUE1. At this time, the fact that the mobile station UE1 has not beenregistered in the MME1 is stored in the storage unit (memory) of theS-GW1.

In a step 7 of FIG. 11, the mobile station UE1 is not registered in theMME1 and only the IMS control bearer is maintained in the S-GW1 and inthe P-GW1. This completes the second stage.

If the third stage, shown in FIG. 12, has not been carried outthereafter, the S-GW1 removes the entirety of bearers (IMS controlbearer resources) that the S-GW1 maintains in connection with the mobilestation UE1, on timeout of the timer whose operation was started at thestep S6 of FIG. 11.

<Third Stage>

FIG. 12 is a sequence diagram showing the operation of a third stage incase a signal has arrived in the second stage from the PDN such as IMS.The following describes respective stages.

In a step 1 of FIG. 12, a notification from the IMSI, indicating theincoming of voice services to the mobile station UE1, arrives at theG-SW1.

In a step S2 of FIG. 12, the G-SW1 stores the information that themobile station UE1 is in an unregistered state due to the restarting ofthe MME1. Hence, the G-SW1 sends a downlink data notification (DownlinkData Notification), inclusive of the IMSI and the previously registeredTA List, to the MME1, to inform the incoming.

If, in a step S3 of FIG. 12, the mobile station UE1, having the IMSIthat has been notified, is not attached, the MME1 performs paging of themobile station UE1 for the received TA List, using the IMSI. However,there is such a case wherein, in carrying out the step S3, the mobilestation UE1 has already selected another S-GW and has attached to theMME1. In this case, to prompt the S-GW1 to release the entirety of thebearers relevant to the mobile station UE1, the MME1 returns a downlinkdata notification acknowledge (Downlink Data Notification Acknowledge)response indicating the cause that the UE1 has already attached.

In a step 4 of FIG. 12, the mobile station UE1 performs the attachmentoperation on receipt of the paging employing the IMSI.

The attach operation of the mobile station UE in the step 4 of FIG. 12is well-known to those skilled in the art and, not directly relevant tothe present invention. Hence, explanation of the detailed configurationis dispensed with.

When the S-GW detects the restarting of the MME, if the tunnel (GTP-U)on the S1-U interface between the eNodeB and the S-GW is active, theS-GW releases the tunnel.

Exemplary Embodiment 2

As an exemplary embodiment 2 of the present invention, the followingdescribes the operation at the time of SGSN restarting in the networkconfiguration of FIG. 7. Basically, the operation of the exemplaryembodiment 2 is equivalent to the operation at the time of restarting ofMME in the exemplary embodiment 1. In the example of FIG. 7, 2G/3G isaccommodated. Specifically, the eNodeB 102 and the MME 103 of FIG. 6 arereplaced by a 2G/3G radio control apparatus (nodeB and RNC) 110 and anSGSN 111. An interface between the 2G/3G radio control apparatus (NodeBand RNC) 110 and the SGSN 111 is Iu, an interface between the 2G/3Gradio control apparatus (NodeB and RNC) 110 and the S-GW 104 is S12, aninterface between the SGSN and the S-GW is S4 and an interface betweenthe SGSN 111 and the HSS 106 is an S6d/Gr.

The operation of the present exemplary embodiment may be summarized tohave three separate stages.

<First Stage>

FIG. 13 is a sequence diagram showing a stage of registering thelocation registration area information of the mobile station UE in theS-GW1, as a first stage. The following describes respective steps.

In a step S1 of FIG. 13, the mobile station UE1 sends a locationregistration request (Attach Request/Routing Area Update Request) to theSGSN1. The Routing Area Update Request is a location registration updaterequest to the SGSN.

In a step S2 of FIG. 13, the SGSN1 newly assigns the locationregistration area information (RAI) to the mobile station UE1.

In a step 3 of FIG. 12, the SGSN1 notifies the S-GW1 of the RAI of themobile station UE1. The S-GW1 maintains the RAI notified as theregistration information of the mobile station UE1.

The location registration operation of FIG. 12 is known per se amongthose skilled in the art and is not directly relevant to thesubject-matter of the present invention. Hence, the configuration is notexplained in detail.

<Second Stage>

FIG. 14 is a sequence diagram for the stage of maintaining a bearer, asa second stage. The following describes respective steps.

In a step S1 of FIG. 14, the mobile station UE1 has already attached tothe SGSN1, and a various types of bearers have been set up using theS-GW1 and P-GW1.

In a step 2 of FIG. 14, the processing of restarting occurs in theSGSN1. The registration information of the mobile station UE1 attachedis erased.

In a step 3 of FIG. 14, the S-GW1 detects the restarting at SGSN1 byprocessing, such as a health check, by GTP Echo processing.

In a step S4 of FIG. 14, the S-GW1 recognizes the entirety of the mobilestations UE (it is confirmed that the mobile station UE1 is accommodatedin SGSN1).

In case the present invention is applied to the entirety of services,all bearers are maintained in a step 5 of FIG. 14.

In steps 6 and 7 of FIG. 14, bearers are not maintained for the entiretyof the services, as is done in the step 5 of FIG. 11. Instead, just abearer relating to a specific service (IMS service, providing e.g.,voice services, in the following example) is maintained.

After step S4 of FIG. 14 of confirming that the mobile station UE1 isaccommodated in SGSN1, the S-GW1 confirms, in a step 6 of whether or notthere is the IMS signaling bearer among the bearers held by the mobilestation UE1. The IMS signaling bearer is a bearer used for IMS control.In determining whether or not a bearer in question is the IMS controlbearer, the value of a QCI (QoS Class Identifier), which is one of thecontrol elements owned by each bearer, for example, may be used. If theQoS value is ‘5’, for example, a bearer in question is determined to bethe IMS control (IMS signaling) bearer in accordance with Table 6.1.7 ofNon-Patent Document 1 (3PP TS23.203). The bearer in question may thus bedetermined to be a control bearer used for providing voice services. Ifthere is such IMS control bearer, the S-GW1 maintains just such bearer,and locally releases (removes) other bearers in accordance with theoperation of Non-Patent Document 1 (3GPP TS23.007).

In case the IMS control bearer is maintained, the operation of a timer,which on timeout releases the bearer, is started in order to takeaccount of the case where the mobile station UE1 has already attached toanother S-GW1. This timer is necessary to prevent failing to releasebearers that the S-GW1 maintains.

In case, in the above timer, the time equivalent to the time of aperiodic location registration timer included in the mobile station UE1is set, the S-GW1 may wait for incoming of voice services for anecessary minimum time corresponding to the time of the next periodiclocation registration request from the UE1. At this time, the fact thatthe mobile station UE1 has not been registered in the SGSN1 is stored inthe S-GW1.

In a step S7 of FIG. 14, the SGSN1 is in such a state that the mobilestation UE1 has not been registered and that only the IMS control beareris maintained in the S-GW1 and in the P-GW1.

In case thereafter the third stage shown in FIG. 15 is not executed, theS-GW1 removes the entirety of the bearers maintained in connection withthe mobile station UE1 (IMS control bearer resources) at a timeout timepoint of the timer whose operation started in the step 6 of FIG. 14.

<Third Stage>

FIG. 15 is a sequence diagram for illustrating the operation of a thirdstage in case of an incoming from PDN, such as IMS.

In a step S1 of FIG. 15, incoming notification of voice services fromIMSI to the mobile station UE1 gets to the S-GW1.

In a step S2 of FIG. 15, the S-GW1 sends the IMSI and the downlink datanotification (Downlink Data Notification) inclusive of IMSI and RAI thathave been registered in advance to the MME to inform the incoming. It isbecause the S-GW1 stores that the mobile station UE1 is in anon-registered state because of restarting of the SGSN1.

In case the mobile station UE1 that has the notified IMSI, has notattached, the SGSN1 in a step S3 in FIG. 15 performs paging of themobile station UE1, for RAI received, using the IMSI. However, there issuch a case wherein, in carrying out the step S3 of FIG. 15, the mobilestation UE1 has already selected another S-GW and has attached to theSGSN1. In this case, to prompt the S-GW1 to release the entirety of thebearers relevant to the mobile station UE1, the SGSN1 sends back to theS-GW1 a downlink data notification acknowledge (Downlink DataNotification Acknowledge) response indicating the cause that the UE1 hasalready attached.

In a step 4 of FIG. 15, the mobile station UE1 that has received thepaging employing the IMSI performs an attachment operation. Theattachment operation of the mobile station UE of the step S4 of FIG. 15is known per se among those skilled in the art and is not directlyrelevant to the subject-matter of the present invention. Hence, itsdetailed configuration is omitted.

Exemplary Embodiment 3

As an exemplary embodiment 3 of the present invention, the followingdescribes the operation in case of employing an ISR function (LTE/3Glocation registration omitting function) under the network configurationof FIG. 8. In ISR, the mobile station UE registers its location in boththe MME and the SGSN. In case of switching a radio access system betweenLTE and 2G/3G, UE location registration is omitted as long as there isno change in the previously registered location registration area in LTEand that in 2G/3G. FIG. 8 shows a packet communication networkconfiguration accommodating LTE and 2G/3G. This configurationcorresponds to the configuration of FIG. 1 added by a 2G/3G radiocontrol apparatus 110 and an SGSN 111 to be connected to the mobilestation UE 101. The MME 103 is connected to the SGSN 111 via an S3interface, while the MME 103 and the SGSN 111 are connected to the HSS106 via an S6a interface and an S6d/Gr interface. The S-GW 104 isconnected to the SGSN 111 and to the MME 103 via an S4 interface and viaan S11 interface.

<First Stage>

The processing of location registration for the UE1 from 2G/3G, as afirst stage, is shown in FIG. 13. FIG. 10 may apply as regards theprocessing of location registration from LTE. By these two operations,the S-GW1 maintains RAI and TA List as the location registration areainformation. The processing of location registration during the ISRoperation is known per se among those skilled in the art and is notdirectly relevant to the subject-matter of the present invention. Hence,its detailed configuration is omitted.

<Second Stage>

FIG. 16 is an example of a sequence as an operation in case ofrestarting of the MME1 of FIG. 8. FIG. 17 shows an example of a sequenceas an operation in case of restarting of the SGSN1 of FIG. 8

In a step 1 of FIG. 16, the mobile station UE1 has its locationregistered in the MME 1, and a various types of bearers have beenestablished using the S-GW1 and the P-GW1.

In a step 2 of FIG. 16, restarting occurs in the MME1, so that theregistration information of the mobile station UE1 in the MME1 iserased.

In a step 3 of FIG. 16, the S-GW1 detects the restarting of the MME1from processing, such as a health check by the GTP Echo processing.

In a step 4 of FIG. 16, the S-GW1 does not perform releasing of bearersbecause the S-GW1 knows that the mobile station UE1 attached to the MME1has been registered using the SGSN1 and the ISR function. At this time,the fact that the mobile station UE1 is not registered in the MME1 isstored in an internal memory of the S-GW1. However, in case the SGSN 1has already been restarted, the processing according to the presentinvention (processing of maintaining the bearer relevant to the mobilestation UE1) is carried out as is the processing of FIG. 11.

The following describes the operation in case the SGSN1 of FIG. 8 hasrestarted.

In a step 1 of FIG. 17, the mobile station UE1 has its locationregistered in SGSN1, and a various types of bearers have already beenset up using the S-GW1 and the P-GW1.

In a step 3 of FIG. 17, the processing of restarting, for example,occurs in the SGSN1, and the registration information of the mobilestation UE1, which has its location registered, is erased.

In a step 3 of FIG. 17, the S-GW1 detects the restarting of the SGSN 1from processing such as a health check by the GTP Echo processing.

In a step 4 of FIG. 17, the S-GW1 does not perform bearer releasingbecause the S-GW1 knows that the mobile station UE1 attached to the MME1has been registered using the MME1 and the ISR function. Thenon-registration status of the mobile station UE1 in the SGSN1 is storedin the internal memory of the S-GW1. However, if the MME1 has alreadyrestarted, the processing according to the present invention (processingof maintaining the bearer relevant to the mobile station UE1) is carriedout as with the processing of FIG. 14.

<Third Stage>

FIG. 18 is a diagram showing an example of a sequence of the operationin case there is an incoming from the PDN under a condition that theMME1 of FIG. 8 has restarted, as a third stage. FIG. 19 is a diagramshowing an example of a sequence of the operation in case there is anincoming from the PDN under a condition that the SGSN 1 of FIG. 8 isrestarted. FIG. 20 is a diagram showing an example of a sequence of theoperation in case there is an incoming from the PDN under a conditionthat both the MME1 and the SGSN 1 of FIG. 8 are restarted.

In case there is an incoming from the PDN under a condition the MME 1 ofFIG. 8 is restarted, incoming notification of communication servicesfrom the PDN 1 to the mobile station UE1 gets to the S-GW1 in a step 1of FIG. 18.

In a step 2 of FIG. 18, the S-GW1 sends a normal downlink datanotification (Downlink Data Notification) to the SGSN1 to inform theincoming.

In a step 3 of FIG. 18, the S-GW1 sends a downlink data notification(Downlink Data Notification), inclusive of the IMSI and thepre-registered TA List, to the MME1 to inform the incoming. It isbecause the S-GW1 stores the non-registered state of the mobile stationUE 1 on account of the restarting of the MME 1.

In a step 4 of FIG. 18, the SGSN1 performs normal paging (paging of themobile station responsive to the incoming).

In a step 5 of FIG. 18, in case the mobile station UE1 having the IMSIaccording to the notification is not attached, the MME 1 performs pagingof the mobile station UE1, using the IMSI, by referring to the TA Listreceived.

In a step 6 of FIG. 18, paging employing the IMSI is received at LTE,the mobile station UE1 performs an attachment operation.

The following describes a case wherein an incoming from the PDN isperformed under a condition the SGSN has restarted.

In a step 1 of FIG. 19, incoming notification of communication servicesfrom the PDN1 to the mobile station UE1 gets to the S-GW1.

In a step 2 of FIG. 19, the S-GW1 sends a normal downlink datanotification (Downlink Data Notification) to the MME1 to inform theincoming.

In a step 3 of FIG. 19, the S-GW1 sends a downlink data notification(Downlink Data Notification), inclusive of the IMSI and thepre-registered RAI, to the SGSM1, to inform the incoming. It is becausethe S-GW1 stores the non-registered state of the mobile station UE1 onaccount of the restarting of the MME1.

In a step 4 of FIG. 18, the SGSN1 performs normal paging.

In a step 5 of FIG. 18, in case the mobile station UE1 having the IMSIaccording to the notification has not attached, the SGSM1 performs thepaging of the mobile station UE1, using the IMSI, by referring to theRAI received.

In a step 6 of FIG. 19, in case the paging employing the IMSI isreceived in 2G/3G, the mobile station UE1 performs an attachmentoperation.

The following describes a case wherein an incoming from the PDN isperformed under a condition both the MME and the SGSN have restarted.

In a step 1 of FIG. 20, incoming notification of communication servicesfrom the PDN1 to the mobile station UE1 gets to the S-GW1.

In a step 2 of FIG. 20, the S-GW1 sends a downlink data notification(Downlink Data Notification), inclusive of the IMSI and thepre-registered TA List, to the MME1, to inform the incoming. It isbecause the S-GW1 stores the non-registered state of the mobile stationUE1 on account of the restarting of the MME1.

In a step 3 of FIG. 20, the S-GW1 sends a downlink data notification,inclusive of the IMSI and the pre-registered TA List, to the SGSN1, toinform the incoming. It is because the S-GW1 stores the non-registeredstate of the mobile station UE1 which is due to the restarting of theMME1.

In a step 4 of FIG. 20, in case the mobile station UE1 having the IMSIaccording to the notification is not attached, the MME1 performs pagingof the mobile station UE1, using the IMSI, by referring to the TA Listreceived.

In a step 5 of FIG. 20, in case the mobile station UE1 having the IMSIaccording to the notification is not attached, the SGSN1 performs pagingof the mobile station UE1, using the IMSI, by referring to the RAIreceived.

In a step 6 of FIG. 20, when receiving the paging employing the IMSI,the mobile station UE1 performs an attachment operation.

The attachment operation of the mobile station UE of the step S6 ofFIGS. 11, 12 and 13 is known per se among those skilled in the art andis not directly relevant to the subject-matter of the present invention.Hence, the detail configuration is omitted.

Exemplary Embodiment 4

FIG. 9 is a diagram showing a network configuration according to afourth exemplary embodiment according to the present invention. In FIG.9, there is shown a CSFB (CS Fallback) architecture. Referring to FIG.9, the network includes a mobile station (UE) 101, a base station(eNodeB) 102, an MME 103, an HSS 106, an MSC/VLR 112, a CS network 113and a G-MSC (gateway mobile switch center) 114. The following describesthe operation of voice incoming from the G-MSC 114 as an originatingsource to the mobile station (UE) 101 with reference to FIG. 9.

A signal notifying the incoming is sent from the G-MSC 114 as anoriginating source to the MSC/VLR 112 via the CS network 113. TheMSC/VLR 112 identifies the corresponding MME 103 from the incominginformation to send a paging request message (Paging-Request-Message) tothe MME 103. The MME 103 sends a paging signal to the mobile stationsthat reside in the serving area. This paging signal includes informationindicating that the paging is for CS services. The mobile station UE 101recognizes this information, that is the information that the paging isthat for CS services, and sends a CS service request signal to the MME103. The MME sends a handover command to the UE1. The mobile station(UE) 101 performs handover, while switching to 3G. The mobile stationLIE 101, which has switched to 3G, sends a paging response to theMSC/VLR 112, as a result of which the voice services at the mobilestation to the incoming voice are started. The following describes theoperation when the MME restarts.

The operation according to the present invention may be summarized tohave three separate stages.

<First Stage>

FIG. 21 is a sequence diagram showing, as a first stage, the stage ofregistering location registration area information of the mobile stationUE. The following describes respective steps.

In a step 1 of FIG. 21, the mobile station UE1 makes a locationregistration request for CSFB (Attach Request, TAU Request and so forth)to the MME1.

In a step 2 of FIG. 21, the MME1 newly assigns (delivers) the locationregistration area information (TA List) to the mobile station UE1.

In a step 3 of FIG. 21, the MME1 notifies the MSC1 of the TAU List ofthe mobile station UE1. The MSC1 maintains the TAU List, notified fromthe MME1, as the registration information of the mobile station UE1.

The location registration operation of FIG. 21 is known per se amongthose skilled in the art and is not directly relevant to thesubject-matter of the present invention. Hence, the detailedconfiguration is omitted.

<Second Stage>

FIG. 22 is a sequence diagram showing, as a second stage, the stage ofmaintaining a bearer. The following describes respective steps.

In a step 1 of FIG. 22, the mobile station UE1 has already attached tothe MME1.

In a step 2 of FIG. 22, restarting occurs in the MME1 and theregistration information of the mobile station UE1 is erased.

In a step 3 of FIG. 22, the MSC1 detects the restarting of the MME1 fromprocessing such as a health check by the SCTP.

In a step 4 of FIG. 22, the MSC1 recognizes the entirety of the mobilestations UE attached to the MME1 (it is recognized that the mobilestation UE1 is accommodated in MME1). The above is the second stage.

<Third Stage>

FIG. 23 depicts an example sequence diagram showing, as a third stage,an operation sequence for the case of incoming (voice incoming or SMS,for example) via a CS domain. The following describes respective steps.

In a step 1 of FIG. 23, an incoming notification to the mobile stationUE1 arrives at the MSC1 by e.g., the G-MSC.

In a step 2 of FIG. 23, the MSC1 sends a paging request messageinclusive of IMSI and pre-registered TA List (SGsAP-PAGING-REQUESTmessage) to the MME1 to notify the MME1 of the incoming. It is becausethe MSC1 stores the non-registered state of the mobile station UE1brought about by restarting of the MME1.

In a step 3 of FIG. 23, in case the UE1 having the IMSI notified theretohas not attached, the MME1 performs a paging of the mobile station UE1,using the IMSI, for the TA List received.

However, there is such a case wherein, in carrying out the step S3 ofFIG. 23, the mobile station UE1 has already selected another MSC and hasattached to the MME1.

In this case, to prompt the MSC1 to release the entirety of the bearersrelevant to the mobile station UE1, the MME1 sends back to the MSC1 apaging reject message (SGsAP-PAGING-REJECT message) indicating the causethat the UE1 has already attached.

In a step 4 of FIG. 23, the mobile station UE1, which has received thepaging that uses the IMSI, performs an attachment operation. Theattachment operation of the mobile station UE in the step 4 of FIG. 23is known per se among those skilled in the art and is not directlyrelevant to the subject-matter of the present invention. Hence, theconfiguration is omitted.

In the drawings of the above described exemplary embodiment, only one(P-GW1) is shown as the P-GW for simplicity of explanation. However, aplurality of P-GWs, such as P-GW2, P-GW3 or P-GWN, may be used in asimilar manner.

Another one of modes of the present invention will now be explained withreference to FIG. 24, which supplements FIG. 10, for example, and showssubscriber data re-installation by network triggered service request. Itis noted that the eNodeB is omitted in FIG. 24.

S1) The MME sends the latest TA-list to a relevant S-GW. That is, theMME informs the latest TA-list on a per UE basis to one or more S-GWs inevery occurrence of mobility events. This information (TA list) isimportant in case of MME failure because paging of the IMSI for thecoverage of the MME in its entirety may thereby be avoided. Since largernumbers of eNodeBs are accommodated in one MME, the load in the EPSsystem may become tremendously severe if paging is to be performed forthe entire coverage.S2) The MME performs restarting.S3) With a restart counter increased by one, a GTP Echo message (GTP-V2Echo response message) is sent to the entirety of the relevant S-GWs.S4) The relevant S-GW detects MME failure by this GTP echo mechanism.The S-GW is able to maintain all or selected bearers, IMSI and the TAlist. An operator is able to select a bearer based on top-rank services(IMS) (service on top (IMS)), as a result of which the bearer maintainedmay be selected only for important services. For other (selected)bearers, the current MME restarting mechanism is applied. If the S-GW isto maintain bearer resources, IMSI and the TA list, the S-GW starts atimer that controls a time interval for maintaining bearer resources,for example. On timeout of the timer, the bearer resources maintainedare removed. This alternative is needed for such case in which, when theUE re-attaches to a network, the S-GW in question is not selected. Thatis, on timeout of the timer of the S-GW in question, the above mentionedbearer resources maintained, for example, S5/S8 bearers, which arespecific bearers maintained, are removed on the assumption that the UEhas re-attached to the network via a S-GW different from the S-GW inquestion.S5) DL data arrives at the P-GW from an external network (PDN).S6) The S-GW acquires the DL data from the P-GW.S7) The S-GW sends a downlink data notification message inclusive of theIMSI and the TA list (DL data notification (IMSI, TA list)) to the MME.S8) The MME starts the IMSI page ((Page (IMSI) to TAs specific in TAlist) for all of TAs of the TA list received from S-GW.S9) On receiving the IMSI page, the mobile station UE1 starts the attach(ATTACH) procedure.S10) On receiving the attach (ATTACH) request from the UE, the MME sendsa location information update request to the HSS.S11) The HSS sends location information update acknowledge to the MME.S12) The MME sends the ATTACH acceptance to the mobile station UE viaeNodeB.

In case of detecting the restart of the MME, the S-GW maintains thebearer, IMSI or the TA list. In this manner, it is possible toinstantaneously recover communication services after restart of the MMEand after arrival of the DL data at the UE from the PDN side.

In a mode of the present invention, in case only the selected bearer isto be maintained, it is possible to suppress consumption of S-GWresources. In addition, by selecting and maintaining bearers forimportant services, communication services may instantaneously berestored for services of higher rank of importance, such as voicecommunication, on arrival of an incoming to the mobile station, afterthe restarting of the MME.

In another mode of the present invention, in case a bearer is to bemaintained by itself or together with the IMSI and the TA list, the timeinterval of the maintenance is managed by a timer. On timeout of thetinier, the bearer, IMSI and the TA list maintained are released. By sodoing, in case, after restart of the MME, the mobile station moves andattaches to a G-SW different from the S-GW that maintains the bearer, itis possible to prevent the S-GW that maintains the bearer frommaintaining the bearer longer than is necessary.

According to the present invention, described above, the followingeffects may be realized.

UE's communication services may be improved in availability by addingpacket incoming as a re-registration trigger of a UE registered in theMME/SGSN in which restarting occurred.

In case the present invention is applied to all services, incoming ofthe entirety of the packets may be used as a trigger for restoring theUE to the network. It may however be thought that many resources on theS-GW side are used, and that location registration events may becomeconcentrated. The S-GW1 is able to maintain the TA list and to performthe Paging processing by using the TA list. However, if it is notpossible for the S-GW to receive the TA list from the MME1, the pagingmay be performed for the whole area supervised by the MME1. In thiscase, many of the radio network side resources would be consumed.

According to the present invention, the S-GW1 is able to maintain theRAI and to perform Page processing by using the RAI. If it is notpossible for the S-GW1 to receive the RAI from the SGSN1, paging may beperformed for the total areas supervised by the SGSN. In this case, manyof the radio network side resources would be consumed.

The disclosures of the aforementioned Non-Patent Documents areincorporated by reference herein. The particular exemplary embodimentsor examples may be modified or adjusted within the gamut of the entiredisclosure of the present invention, inclusive of claims, based on thefundamental technical concept of the invention. Further, a various typesof combinations or selection of elements disclosed herein may be madewithin the framework of the claims. That is, the present invention maycover a wide variety of modifications or corrections that may occur tothose skilled in the art in accordance with the entire disclosure of thepresent invention, inclusive of claim and the technical concept of thepresent invention.

EXPLANATIONS OF SYMBOLS

-   101 UE-   102 eNodeB-   103 MME-   104 S-GW-   105 P-GW-   106 HSS-   107 S5/S8-   108 external network-   109 IMS-   110 2G/3G radio control apparatus (NodeB/RNC)-   111 SGSN-   112 MSC/VLR-   113 CS network-   114 G-MSC (gate mobile switch center)

What is claimed:
 1. A mobile communication system, comprising a userequipment (UE), a mobility management entity (MME), and a mobileswitching center/visited location register (MSC/VLR), wherein the MME,upon reception of an SGsAP-PAGING-REQUEST message regarding aninternational mobile-station subscription identifier (IMSI) from theMSC/VLR as a paging request message, sends the paging request messageincluding location information provided by the MSC/VLR to page the US.2. A mobility management entity (MME) used in a mobile communicationsystem that comprises a user equipment (UE) and a mobile switchingcenter/visited location register (MSC/VLR), the MME comprising: a pagingunit that, upon reception of an SGsAP-PAGING-REQUEST message regardingan international mobile-station subscription identifier (IMSI) from theMSC/VLR as a paging request message, sends the paging request messageincluding location information provided by the MSC/VLR to page the UE.3. A user equipment (UE) used in a mobile communication system thatcomprises a mobility management entity (MME) and a mobile switchingcenter/visited location register (MSC/VLR), wherein the MME, uponreception of an SGsAP-PAGING-REQUEST message regarding an internationalmobile-station subscription identifier (IMSI) from the MSC/VLR as apaging request message, sends the paging request message includinglocation information provided by the MSC/VLR so that the UE is paged bythe MME.
 4. A communication method in a mobile communication system thatcomprises a user equipment (UE), a mobility management entity (MME) anda mobile switching center/visited location register (MSC/VLR), thecommunication method comprising: by the MME, upon reception of anSGsAP-PAGING-REQUEST message regarding an international mobile-stationsubscription identifier (IMSI) from the MSC/VLR as a paging requestmessage, sending the paging request message including locationinformation provided by the MSC/VLR to page the UE.
 5. A communicationmethod of a mobility management entity (MME) used in a mobilecommunication system that comprises a user equipment (UE) and a mobileswitching center/visited location register (MSC/VLR), the communicationmethod comprising: by the MME, upon reception of an SGsAP-PAGING-REQUESTmessage regarding an international mobile-station subscriptionidentifier (IMSI) from the MSC/VLR as a paging request message, sendingthe paging request message including location information provided bythe MSC/VLR to page the UE.
 6. A communication method of a userequipment (UE) used in a mobile communication system that comprises amobility management entity (MME) and a mobile switching center/visitedlocation register (MSC/VLR), the communication method comprising: by theMME, upon reception of an SGsAP-PAGING-REQUEST message regarding aninternational mobile-station subscription identifier (IMSI) from theMSC/VLR as a paging request message, sending the paging request messageincluding location information provided by the MSC/VLR; and by the UE,being paged by the MME.
 7. The mobile communication system according toclaim 1, wherein the MME has restarted.
 8. The mobile communicationsystem according to claim 1, wherein the location information includeslocation registration area information.
 9. A mobile communicationsystem, comprising: a mobility management entity (MME) or a serving GPRS(General Packet Radio Service) support node (SGSN); and a servinggateway (SGW), wherein the SGW, upon detection of restart of the MME orthe SGSN, maintains a specific S5/S8 bearer resource appropriate fornetwork triggered service restoration and deletes all other S5/S8 bearerresource.
 10. A serving gateway (SGW) used in a mobile communicationsystem that comprises a mobility management entity (MME) or a servingGPRS (General Packet Radio Service) support node (SGSN), the SGWcomprising: a unit that, upon detection of restart of the MME or theSGSN, maintains a specific S5/S8 bearer resource appropriate for networktriggered service restoration and deletes all other S5/S8 bearerresource.
 11. A user equipment (UE) used in mobile communication systemthat comprises: a mobility management entity (MME) or a serving GPRSsupport node (SGSN); and a serving gateway (SGW), the UE comprising: aunit that reattaches to the mobile communication system in response to apaging from the mobile communication system with the SGW maintaining,upon detection of restart of the MME or the SGSN, a specific S5/S8bearer resource appropriate for network triggered service restorationand deleting all other S5/S8 bearer resource(s).